Dictograph



AL. scHEn. DICTDGRAPH.

APPLICATlON FILED FEB. 26. |918.

Patented Uct. 7, 1919.

LOUIS SCHEB, OF NEW YORK,

N. Y., ASSIGNOR, BY MESNE ASSIGNMENTS, TO DICTO- 'GRAPH PRODUOTS CORPORATION, A CORPORATION OF VIRGINIA.

DIOTOGBAPH.

Specioation of Letters latent.

Patented Oct. '7, 1919.

Application led February 26, 1918. Serial No. 219,215.

To all whom 'it may concern.'

Be it known that I, Louis Semin, a citizen of the Unit/ed States, residing at the city of New York, in the borough of Bronx and State of New York, have invented certain new and useful Improvements in Dictographs, of which the following is a full, clear, and exact description.

This invention relates to the dictograph or detective telephone, the primary.object being to provide means whereby the transmitter of 4an ordinary service telephone may be used as the transmitter of a dictograph circuit without apparent evidence that the service telephone has been adapted for such use.

The ordinary dictograph or detective telephone comprises a simple circuit containing a battery, a transmitter and a receiver, the transmitter being usually located in a room or apartment where conversation is to be carried on which itis desired to hear, the instrument being hidden or placed in some inconspicuous lace where its presence will not be detect-ed Ey the persons subjected to the espionage. The receiver is placed in any other convenient locality where the transmitted conversation may be heard Without the knowledge of the persons speakhe dictograph has become of such unversal use that dishonest persons and sometimes others who do not Wish their conversation to be overheard often make a search for a hidden transmitter before they indulge in conversation, and since these conversations very often, if not usually, occur in business offices where an ordinary service telephone is installed, it is apparent that if such telephone could. be used as a part of the dictograph system without so altering the service tele hone as to give rise to the suspicion that it was being used for dictograph purposes, it would constitute a valuable addition to the dictograph art.

My invention therefore consists broadly in combining the dictograph circuit with the sei-vice telephone circuit in such a manner that the combination cannot be detected by ordinary observers. The manner of accomplishing this will be described in connection with the accompanying drawing, in which the figure is a diagram of the circuits and instruments comprised in a service telephone substation and a dictograph receiving station connected for cooperation, as contemplated by my invention.

The ordinary service tele hone substation now commonly used comprises a'stationary call-box-to which the two wires of the external circuit lead and which contains the ordinary signal operated from the central oliice to summon the subscriber, and a portable telephone set comprising a transmitter, a receiver and a hook switch or its e uivalent, which are mounted upon a stan in a manuel' to be conveniently held in the hand when 1n use, this stand being connected with the stationary call-box by means of e single cable carrying the various conductors required for the service.

In the drawing, l indicates the call-box to which the two external Wires 2 and 3 lead and are permanently connected at binding posts 4 and 5, respectively. The bell is conventionally represented at 6 and is operated in the usual manner, it having nothing todo with the present invention. The portable telephone set, which is understood to be mounted upon a portable stand convement to be handled, but which is not shown, consists of the transmitter T, the receiver R and the hook switch S. Three conductors ordinarily extend from the call-box to the portable set. These are represente by 7,. 8 and 9, respectively, being attached to binding pos-ts 10, ll and 12 in the box, the conductor 7 leading to one side of the transmitter and thence by wire 13 to the switch lever, the conductor 8 leading to one side of the receiver, and thence by wire 14 to one of the contacts 15 of the switch, and the wire 9 leading to a second switch contact 16. With the receiver R on the hook, the circuits of the two instruments are open, as usual, the onl closed circuit being from the central o ce through the signal in the box. The three conductors 7, 8 and 9 are usually combined into a single flexible cable having the familiar green silk insulation or covering. In order to convert this telephone substation for dictograph purposes it is only necessary to add one conductor to the cabh` connmting the box with the portable set und I contemplate doing this by removing thc original three-couductor cable entirely and substituting a four-conductor cable, which will also be provided with the green silk insulation so that it will have the same external appearance as the original cable and will differ therefrom only in that it will be slightly larger in diameter, a fact which would not be discovered by the ordinary observer. In substituting this four-conductor-cable for the original cabie, three of the wires will be connected respectively with the box and the instruments, exactly as the three wires 7, 8 and 9 are connected, while the fourth wire indicated by 17, will be permanently connected in the portable set with the wire 13 at some oint between the transmitter and the switcli lever, while in the box its end will remain loose for connection with one of the wires of the dicto rapli circuit. At the receiving end of the dictograph circuit there is located a telephone receiver R', a battery B and a rlieostat r. These devices will ordinarily be contained in a portable box (not Shown) havin two binding posts 18 and 19 between which the several dc- \iccs are connected in series. The devices are then connect-ed with the service telephone by running one conductor 20 from post. 18 to post 4 of the call-box, with which the main conductor 2 is connected. Another wire 21 is run to the call-box and connected with the loose end of the wire 17 therein. Conductor 20 connects with conductor 7 by way of the permanent connection 22 between the posts 4 and 10. It will thus be seen that the twowires 2O and 21 are permanently connected to the respective terminals of the transmitter T of the service telephone and' that this connection is not affected in any manner by the o eration of the hook switch.

The receiver of the dictograph is a supersensitive .instrument capable of re;- spondin to and reproducing any sounds delivere to the transmitter T even though the source of the sound is somewhat distant from the transmitter. Persons entering a room for the purpose of a conference will ordinarily take seats at a desk or table adjacent to which the Service telephone is installed, and will thus be located at only short distances from the transmitter. lTo such persons the converted telephone will ive no indication of its conversion, and w ile the telephone remains on the hook it will be supposed by such persons that the telephone is inoperative to convey their conversation. As a matter of fact, however, it will be seen that notwithstanding that the receiver is on the hook an sounds delivered to the trans` initter will lise conveyed to the receiver R' by the battery B, over the following circuit: from transmitter T, by wire 7, wire 22, wire Q0, post 18, rheostat r, battery B, receiver R', post 19, wire 21, wire 17 and wire 13, to transmitter.

The function of the rlieostat v' at tlie receiving end is to enable the listener to ad- ]ust the resistance of the circuit for thebest effect upon the receiver R. The length of the wires 20 and 21 will yary with different installations and the rheostat is used to conipensate for these variations.

The term hook switch is used herein to cover any switch that normally holds the circuit of the transmitter and receiver of the substation open, but which closes those circuits while conversation is carried on; hence whether such switch be gravity or manually operated is immaterial.

I claim:

1. A subscribers telephone station including a switch controlling the normal circuits of the station transmitter and receiver. in combination with another receiver and a circuit including the same and the station transmitter and excluding the switch.

2. .A subscribers telephone station including a switch controlling the normal circuits of the station transmitter and receiver, in combination with a circuit including another receiver, a battery and the station transmitter and excluding the switch.

3. A telephone substation comprising a portable transmitter and receiver set, a hook switch and a si nal box connected therewith by a single mu tiple conductor cable, two of the conductors of said cable extending to the respective terminals of the transmitter independent of the hook switch and affording a permaneiitlyrclosed portion of a circuit including the transmitter.

4. A telephone substation comprising a portable transmitter, receiver and hook switch, a stationary call-box and a single multiple conductor cable connecting the set withl the box, three wires of said cable extending to the transmitter, one of which is norma ly open at the hook switch while the other. two are'permanently closed, in coinbination with a second receiver in circuit 'with said permanently closed wires.

5. A telephone substation comprisin a transmitter, receiver and switch, a call ox and appluralit of conductors connecting the set wi .li the ox, three of said conductors extendin to the transmitter, one of' which is norma ly open at the switch wlile the otherl two are permanently closed, in combination with a second receiver in circuit with said permanently closed wires.

In witness whereof, I subscribe my sig'- nature.

LOUIS SCHER. 

